1,721,140 research outputs found
Contributo allo studio climatico e bioclimatico delle stazioni di leccio (Quercus ilex L.) del Veneto e del Trentino meridionale.
No full textValutazione della qualità della vegetazione della torbiera delle Viote del Monte Bondone (TN) con lineamenti di corretta gestione ambientale.
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The response of plant community diversity to alien invasion: Evidence from a sand dune time series
No full textThis study examines the process of invasion of coastal dunes in north-eastern Italy along a 60-year time series considering alien attributes (origin, residence time, invasive status, and growth form strategy) and habitat properties (species richness, diversity and evenness, proportion of aliens, and proportion of focal species). Vegetation changes through time were investigated in four sandy coastal habitats, using a fine-scale diachronic approach that compared vegetation data collected by use of the same procedure, in four time periods, from the 1950s to 2011. Our analysis revealed an overall significant decline of species richness over the last six decades. Further, both the average number of species per plot and the mean focal species proportion were proved to be negatively affected by the increasing proportion of alien species at plot level. The severity of the impact, however, was found to be determined by a combination of species attributes, habitat properties, and human disturbance suggesting that alien species should be referred to as “passengers” and not as “drivers” of ecosystem change. Passenger alien species are those which take advantage of disturbances or other changes to which they are adapted but that lead to a decline in native biodiversity. Their spread is facilitated by widespread anthropogenic environmental alterations, which create new, suitable habitats, and ensure human-assisted dispersal, reducing the distinctiveness of plant communities and inducing a process of biotic homogenization
Pollinator distribution in patches of suitable habitat depends more on patch isolation than on floral abundance
Full text linkIntrinsic complexity of real-world systems makes particularly difficult to decipher which factors influence the dispersal of pollinators in the landscape matrix and their distribution among patches of suitable habitat.
Saltmarshes are an ideal and naturally simplified landscape to study the ability of different groups of pollinators to disperse across a landscape matrix, as they consist of a matrix of flooded areas surrounding patches of suitable habitat with different degrees of isolation from the mainland and different levels of floral abundance. We hypothesise that pollinator distribution to flowering plants depends more on patch isolation than on floral abundance with pollinator richness and visitation rates to flowering plants decreasing with increasing distance from the mainland. To this end, we established 60 permanent plots at varying distances from the mainland and monitored pollinator visitation to entomophilous plants. We also quantified the reproductive success of entomophilous species in the surveyed plots by calculating fruit set. We found that the pollinator community of
saltmarshes consisted only of flying pollinators with good dispersal abilities, while we recorded no flightless pollinator species. Both pollinator richness and visitation rate decreased with increasing distance of patches of suitable habitat from the mainland, affecting reproductive success of a non-autogamous entomophilous species.
Interestingly, floral abundance did not affect pollinator richness and visitation rate to flowering plants, nor did it affect reproductive success of target plant species. In saltmarshes, the pollinator distribution depends more on patch distance from the mainland than on floral abundance. Our results suggest that the presence of patches of suitable habitat in a landscape matrix does not necessarily ensure the maintenance of pollinators. Rather, our results suggest that suitable habitat isolation is the critical factor in pollinator dispersal and distribution that should be considered to improve landscape matrix permeability to pollinators
The co-occurrence of different grassland communities increases the stability of pollination networks
Full text linkHigh heterogeneity of grassland communities supports a high diversity of species and represents a key point for
the retention of pollinators in agricultural landscapes. In the present study, we explored whether the co-occurrence
of different grassland communities has any effect on the stability of the network of pollination interactions.
We monitored pollination interactions in two co-occurring grassland communities, differing in disturbance
history and water and nutrient supply. The monitoring was carried out during the summer season (7
surveys). For each survey we compared the role in the pollination networks (i.e., keystone vs. peripheral species)
of habitat-specialist and habitat-generalist plant and pollinator species. We found that plant and pollinator
species of the two different grassland communities were highly interconnected, revealing that pollination interactions
occur at a level of organization above that of the single community. The co-occurrence of the two
grassland communities increased the type, number and frequency of contacts, thereby contributing to networks
stability. The role of habitat-specialist and habitat-generalist plant and pollinator species in pollination networks
was asymmetric, with habitat-specialist plants and habitat-generalist pollinators being keystone species, while
habitat-generalist plants and habitat-specialist pollinators being peripheral in the pollination networks. Our
results showed that the stability of the network does stem from the co-occurrence of different species pools
having different but complementary roles in the pollination networks. From a conservation perspective, the
maintenance of different grassland communities is important not only because they allow the conservation of
habitat-specialist species, but specifically because plant species specialized in either grassland community are
also keystone for the maintenance of the stability of the pollination networks
Are the ancient forests of the Eastern Po plain large enough for a long term conservation of herbaceous nemoral species?
Full text linkWe analysed the effects of patch configuration and site history on vascular plants in ancient forests of the Eastern Po Plain, documented back to 1740. Despite their reduced size, all the forests are part of Natura 2000 Network and significantly contribute to the maintenance of a threatened habitat and
support biological diversity of the Continental biogeographic region. The presence of some functional ecological plant species groups was correlated with patch configuration and age. Habitat
quality, in terms of suitability for forest species, was found to be important in explaining the presence of species of high conservation value, but patch age (as an indicator for habitat quality) played a major role too. For core forest species, patch area is a redundant variable in explaining species richness relative to habitat quality and patch age and the extinction of specialists seems to occur mainly in a deterministic way. Even small forest fragments can be very important for maintaining plant species diversity, at least if they are of high habitat quality and if the forest management is appropriate. However, to achieve a long term conservation, management plans should also aim at an improvement of the anthropogenic matrix surrounding forest remnants
Primo contributo alla conoscenza dell'ecologia di Robinia pseudoacacia L. sui Colli Euganei (PD).
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